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Behind the Headlines

Wellness &Learning

Sleep Deficits

Scientists are learning why a lack of sleep is bad for our health

Evidence shows that a lack of sleep can have a negative impact on our health, increasing the risk for accidents as well as health problems like obesity, infections, and heart disease. Extensive research is beginning to give scientists clues as to why this might be so. Sleep plays a critical role in how well we concentrate and perform, helps consolidate memories and set the stage for learning, and may affect how the immune system responds to attack. Teasing apart patterns like these will help us understand why we sleep and how sleep helps keep us healthy.

An apple a day may keep the doctor away, but can the same be said for 40 winks a day? Losing sleep can leave you more than just a little cranky. Evidence is building that sleep may have a fundamental role in keeping you healthy and in fighting off disease.

In fact, sleep loss can have as big an effect on performance as drinking. One study showed that truck drivers who had gone 28 hours without sleep performed as poorly as if they had blood alcohol levels of 0.1 percent, which is above the legal limit in much of the world.

Sleep is also important for our emotional health. Students who reported getting significantly less sleep on school nights in one study, for example, were more likely to say they felt hopeless, sad, or depressed.

Illness and sleep are linked in other ways as well. Injury or infection tends to increase the amount of time we sleep and can disrupt normal sleep patterns. In addition, heart attacks and strokes happen more often in the morning than at other times of the day, which may be linked to natural changes in body rhythms, including our regular cycles of sleeping and being awake.

Proper sleep also may help us maintain a healthy weight. Many studies show that inadequate sleep puts people at an increased risk of becoming overweight. Some also note a connection between longer sleep times and being overweight. Recent research tracking hormone levels may help scientists understand why.

Researchers following more than 1,000 people found that those who slept for five instead of eight hours had 15 percent lower levels of leptin and 15 percent higher levels of ghrelin. These two hormones regulate how hungry you feel, and lower levels of leptin and increased ghrelin both increase appetite. An ongoing study is following a group of overweight subjects to study the impact sleep has on hormone levels and weight.

Many scientists studying the role of sleep in maintaining good health are also taking a close look at inflammation. Recent experiments indicate that when we fail to get enough sleep, inflammation may result. For example, one study showed that people who got only 4.5 hours of sleep 10 days in a row had levels of a protein marker for inflammatory processes that were three times higher at the end of that period than at the beginning. The protein, C-reactive protein, has been shown to predict the risk of stroke and heart attack. The elevated levels put some of the study’s subjects in the high-risk range.

Another line of research has examined cellular chemicals known as cytokines, which are among the first signals the body sends out in response to infection and injury. Based on a number of studies in animals, researchers suspect that cytokines known to cause inflammation also enhance sleep. Other cytokines that block inflammation tend to inhibit sleep. Taken together, these patterns give researchers hints as to why being sick makes us feel tired.

While the complicated interrelationships that connect sleep and health have not yet been fully mapped out, additional research may one day help us gauge what is a “healthy” amount of sleep. Evidence points to finding a happy medium for sleep: Too little — or too much — increases the risk of disease, and may even shorten your life. That makes those 40 winks a day as important as that apple.

First published in the United States by the Society for Neuroscience, Washington, D.C. Copyright 2007. All rights reserved. www.sfn.org